Containers made of thermoplastic materials, for example, polyethylene terephthalate (PET) are popularly used in various industries including cosmetic, laundry, and food industries. Containers having a pearlescent appearance are appealing to consumers. Consumers are more likely to buy products packaged within a pearlescent container since such containers tend to connote that a premium product is contained inside. Some particles including pearlescent mica, aluminum oxide, silicon dioxide and glass fibers have been reported as being mixed with thermoplastic materials to make a pearlescent container, for example in JP patent publication 2004-18629 by Fujitsu Limited. The pearlescent effect of the container surface disclosed herein is achieved by the light interference effect on such particles. However, the use of such particles is undesirable for a few reasons.
One reason is that the incorporation of such particles can negatively affect the surface smoothness of the container. Another reason is that the container surface is more likely to have unwanted weld lines and flow lines. A weld line is formed when separate melt fronts of the melted thermoplastic materials traveling in opposite directions meet. A flow line occurs if two emerging melt fronts flow parallel to each other and create a bond between them. These lines are undesirable from both an aesthetic and container strength point of view. Besides, such particles may also affect the recyclability of the bottle.
Other methods have been offered to provide a pearlescent appearance to container. Various combinations of thermoplastic materials have been reported to provide a pearl gray or so-called pearl-like appearance of a thermoplastic article. Such mixtures include the combinations of polyester and methacrylic, polypropylene and nylon, polyester and polymethyl pentene, as those disclosed in JP patent publication 56056831A by Mitsubishi Rayon Co. Ltd, JP patent publication 2004292037A by Toppan Printing Co. Ltd and EP patent publication 0456929A by Shiseido Co. Ltd. The use of such thermoplastic material combinations may also pose processing difficulties, including that caused by the un-matching melting points of two or more thermoplastic materials, which consequently requires the addition of compatibilizers to overcome this problem. Separately, some thermoplastic materials in the combination are chemically active, for example, methacrylic, which may compromise the stability of the container made therefrom.
Silicone has been reported as being used in making various thermoplastic articles for improving mechanical strength, for improving lubricity of a thermoplastic article, and useful as a processing aid. For example, as disclosed in U.S. Pat. No. 5,708,084 by Dow Corning, US patent publication 2008/0167597A1 by Playtex Products, Inc and JP patent publication 2004-018629A by Fujitsu
Therefore, there is still a need for the development of a container which has a pearlescent appearance but which is without the shortcomings of the prior art.